ScriptReference/SceneManagement.Scene-path

[docscomments[bot]]

ScriptReference/SceneManagement.Scene-path

https://docs.unity3d.com/ScriptReference/SceneManagement.Scene-path.html

[houkanshan]

Could be null if the scene is not loaded before, especially when you use it in editor.
Use this instead:
SceneUtility.GetScenePathByBuildIndex(0);

[FreyaHolmer]

This is an empty string for new/untitled/unsaved scenes that don't have a corresponding scene asset saved yet, which is a useful way to check that very thing, since IsValid() still returns true for scenes without a corresponding scene asset